“Invisibility cloak” for surfers: researchers find new solutions to keep sharks away

Scientists have discovered that equipping surfboards with bright LED lights could deter great white shark attacks on surfers and swimmers. A recent study published in the journal Current Biology found that illuminating the underside of surfboards disrupts the silhouette perceived by sharks, making it less likely for them to mistake humans for their usual prey, such as seals.

The research was led by Dr. Laura Ryan, a biologist at Macquarie University in Sydney, Australia, who specializes in comparative neurobiology and is an avid surfer herself. Dr. Ryan, along with Professor Nathan Hart, head of the Macquarie University School of Natural Sciences, spent six years conducting experiments in the waters of Mossel Bay in South Africa, a popular feeding ground for great white sharks.

Great white sharks often attack their prey from below, and due to their far lower visual acuity compared to humans, they can easily mistake the silhouette of a surfer or swimmer for that of a seal. "There was a big spate of shark bites and as a really keen surfer I was spending a lot of time thinking about sharks' eyesight," Dr. Ryan said. She began pondering how her research on shark vision could be used to protect people from shark attacks. "I started to think what if what I was learning could potentially protect surfers?" she added.

To test their theory, the research team towed seal-shaped decoys equipped with different configurations of LED lights behind a boat in waters known to be inhabited by great white sharks. They experimented with various light treatments on the decoys, including dim, intermediate, and bright LED lighting, as well as different patterns such as horizontal and vertical stripes, continuous lighting, and strobe effects.

The study found that brighter lights on the underside of the decoys were more effective in deterring great white sharks, with the brightest lights being the most effective. The unlit decoys were attacked or followed by sharks more than any of the illuminated decoys, indicating that brighter decoys led to less interaction. "The most critical thing was that the brightness on the decoy had to be brighter than or equal to the background light. As long as the lighting stopped the silhouette from looking black, it seemed to work," Dr. Ryan explained.

Horizontal stripes of LED lights proved to be particularly effective in breaking up the silhouette of the decoys, making them appear less like prey to sharks. "When you do horizontal stripes, the silhouette [appears] wider than it is long, so it's less like a seal," Dr. Ryan said. In every instance where the striped design was used on the decoys, there were no attacks. Vertical lights, however, were less effective, possibly because they broke the silhouette into longer sections that could still be identified as a seal.

The research team also found that strobe lighting was less effective than continuous lighting, as it gave the sharks momentary glimpses of the decoy silhouette, leading to increased interaction with the objects. "Interestingly, just that small glimpse of the entire silhouette was enough for the white sharks to start biting the decoys," Dr. Ryan noted.

Professor Nathan Hart commented on the findings, stating, "It's like an invisibility cloak but with the exception that we are splitting the object, the visual silhouette, into smaller bits." He added, "So we think this tells us a lot about how sharks see the world and how they detect and target their prey. But it also potentially gives us an insight into how we can develop a non-lethal shark deterrent especially for surfers."

The researchers are now in the process of building prototypes for use on the underside of kayaks and surfboards, including embedding LEDs into surfboards. "What we're trying to do now is move from seal decoys into a surfboard prototype by embedding LEDs into the bottom of a surfboard," Dr. Ryan said. She emphasized the importance of practicality, stating, "As a surfer, I want it to be usable."

Further research is required to determine if the lighting deterrent is effective on other species of sharks, such as bull sharks and tiger sharks, which have different hunting strategies and may not rely on visual cues as much as great whites. "We don't know if it will be as effective on them because we're not certain if they rely on visual cues as much as white sharks," Dr. Ryan said.

Globally, most fatal shark bites and attacks are due to great white sharks, which do not consider humans as prey but may mistake them for seals. In Australia, great white sharks have been responsible for 94 of the 255 fatal shark incidents recorded since 1791, according to official data from the Taronga Conservation Society's database.

The study's findings offer a potential non-lethal method to reduce shark attacks on humans without harming the animals. This could lessen the reliance on other shark deterrent measures such as shark nets and drum lines, which can be destructive to other marine life. By altering the silhouette of surfboards and other watercraft, surfers and swimmers may be able to coexist more safely with sharks in the ocean.

Sources: Mundo, La República, La Croix, France 24, Asharq Al-Awsat (English), Manila Times, Tuu1ed5i Tru1ebb News, Sky News Arabia, ORF Science, The Guardian, New Scientist, ABC News Australia, Gazeta.ru, Sydney Morning Herald, The Age

This article was written in collaboration with generative AI company Alchemiq